Patella Alta on X-Ray and MRI: Diagnostic Agreement and Clinical Correlations
Abstract
Background/Objectives: Patella alta contributes to patellofemoral (PF) maltracking and anterior knee pain, but the agreement of patellar-height indices across imaging modalities and their clinical relevance remain uncertain. We aimed to estimate the prevalence of patella alta when using each index, quantify inter-method agreement, and quantify patella alta's associations with Hoffa's fat-pad impingement, patellar chondromalacia, and tibial tubercle-trochlear groove (TT-TG) distance. Methods: This retrospective cross-sectional study included 250 patients aged 18-38 years who underwent both knee radiography and MRI. Patellar height was assessed using the Insall-Salvati (IS) and modified Insall-Salvati (mIS) ratios on radiographs and MRI, and the Patellotrochlear Index (PTI) on MRI. Associations with fat-pad impingement, chondromalacia grade, and TT-TG abnormality were analyzed using the chi-square or Fisher's exact test and as odds ratios (ORs) adjusted for age, sex, and imaged side; agreement was assessed with Cohen's kappa (κ). Results: Patella alta prevalence was 13.2% using IS on radiographs and 10.8% using IS on MRI, but markedly lower with mIS (≤1.6%). Patella alta was more frequent in patients with Hoffa's fat-pad impingement (31.1% vs. 5.7% on IS radiography; adjusted OR 8.83, 95% CI 3.82-20.45) and advanced chondromalacia (p = 0.025). Agreement was moderate between IS radiography and IS MRI (κ = 0.47, 95% CI 0.33-0.61) and between IS MRI and the PTI (κ = 0.43).…
How strong is the evidence?
Evidence Hub reads this as a cross-sectional, done in people. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause. Reported size: 250 participants or records.
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